(PA-120) Prognostic of Baseline 18F-FDG PET/CT in Transplant-Eligible Patients with Newly Diagnosed Multiple Myeloma

Introduction:  Bone disease is a hallmark of multiple myeloma (MM), and whole-body imaging plays a key role in staging and prognostication. Among available modalities, 18F-FDG PET/CT uniquely combines anatomical and metabolic information. While previous studies have highlighted the prognostic relevance of parameters such as the number of focal lesions and the maximum standardized uptake value (SUVmax), real-world data remain scarce.

Methods:   We conducted a retrospective study including consecutive transplant-eligible patients with newly diagnosed MM (NDMM) who underwent baseline 18F-FDG PET/CT and received bortezomib-based induction therapy (± anti-CD38 monoclonal antibodies), followed by autologous stem cell transplantation (ASCT) and maintenance, according to an intention-to-treat approach. The prognostic value of the number of focal lesions (FL) (as both continuous and categorical variable) and SUVmax at baseline were assessed. Optimal thresholds for predicting 3-year progression-free survival (PFS3) were defined using receiver operating characteristic (ROC) curve analysis. Associations between PET/CT parameters and PFS3 were explored using logistic regression, adjusted for known prognostic factors.

Results:   A total of 124 patients were included (median age: 58 years; range: 39–73), with a median follow-up of 39 months (IQR 20–75). The median PFS was 74 months (95%CI 36.6-62.3), while median overall survival was not reached. ROC analysis identified ≥4 focal lesions as the optimal cutoff to predict PFS3 (AUC 0.59; sensitivity 55.6%, specificity 58.8%); SUVmax ≥9.2 showed limited prognostic utility (AUC 0.50). In univariate analysis, the presence of ≥4 lesions showed a trend toward inferior PFS3 (p = 0.18). However, in multivariate analysis, neither ≥4 lesions (p = 0.47) nor SUVmax ≥9.2 (p = 0.61) were independently associated with PFS3. In contrast, minimal residual disease (MRD) positivity (p = 0.009) and failure to achieve complete response (CR) or stringent CR (sCR) (p = 0.058) were associated with poorer outcomes. Notably, quadruplet induction therapy was significantly associated with a reduced risk of progression at 3 years (p = 0.011).

Conclusions:   In newly diagnosed, transplant-eligible MM patients, baseline PET/CT findings—particularly the number of focal lesions—may provide valuable prognostic insight. Although not independently predictive in multivariate analysis, ≥4 lesions were associated with a trend toward earlier progression. Our findings emphasize the prognostic impact of deep responses (MRD negativity and CR/sCR) and the potential benefit of quadruplet induction therapy in mitigating high-risk disease features such as extensive bone involvement. Further large-scale studies are warranted to refine the role of PET/CT in prognostic models for MM.